Gross and Microscopic Anatomy of the Olfactory Bulbs in the Chinchilla (Chinchilla lanigera)

Abstract

Chinchillas are primarily used as laboratory animals in auditory pathways research, it is necessary to acquire detailed neuroanatomical data on other encephalon segments, in order to assess whether this species might also contribute as olfactory pathways experimental models. Thus, our research focused on providing a gross and microscopic description of the chinchilla’s olfactory bulbs. Five chinchilla encephalon samples were harvested from commercially slaughtered young adults. The pairs of olfactory bulb were isolated by dissection, macroscopically examined while still attached, then detached, fixed in buffered formalin, serially cut and stained using a modified Luxol-Cresyl protocol. Gross and microscopic features were assessed and compared to literature descriptions of related species such as the rat and the rabbit. Chinchillas presented large olfactory bulbs with an average maximal diameter of 3 mm each, positioned in two corresponding deep grooves of the cribriform plate, orally to the anterior limit of the cerebral hemispheres. They decreased in girth ventro-aborally towards their base, which was located on the ventral side of the telencephalon. Histologically, they presented a laminar structure: an olfactory nerve layer, a glomerular layer, an external plexiform layer, a mitral cell layer, an internal plexiform layer and a granule cell layer. The proportionally well developed olfactory bulbs and the existence of the accessory olfactory bulbs demonstrates that C. lanigera is a macrosmatic species. The olfactory bulbs in the chinchilla present the gross anatomy and histological outline concurring with literature rodent descriptions, with certain particularities (accessory bulb topography, olfactory ventricle topography, glomerular size and shape).